Presently known hot beverage vending machines comprise a boiler in which water is heated to predetermined suitable conditions, and further comprise means for conducting said hot water towards a dispenser, which in turn directs the water towards a beverage serving depending upon the beverage selected. Depending on whether or not it is necessary to pressurize the water, a distinction is made between two types of hot beverage machines: powdered beverage machines and soluble beverage machines. Soluble beverage machines serve only hot beverages that do not require pressurized hot water, i.e., they serve beverages made from soluble products such as cocoa, instant coffee, and the like, as well as infusion hot beverages. Said soluble beverage machines are characterized in that the water used in the serving of the product can be used at atmospheric pressure. In contrast, powdered beverage machines alternatively or additionally serve products that require water at a pressure of at least 9 bars in order to prepare them, such as non-soluble ground coffee in its various forms.
In the case of soluble beverage machines, the boiler must be a large-volume stainless steel open boiler. In the case of powdered beverage machines, use is made of a more economical closed, pressurized boiler.
One of the disadvantages associated with hot beverage machines is that the first soluble hot beverage or beverages served after a period of no servings are served at an appreciably lower than usual temperature. This is due to the fact that the residual water in the pipes between the boiler and the dispensers as well the pipes themselves and other elements such as valve seats, which generally consist of bulky brass bodies, cool down after a certain period of time so that the first serving or servings after this period yield part of their heat to heat all of the aforementioned elements to the design conditions.
Solutions to this problem have been proposed, such as, for example, establishing either a periodic or a temperature-controlled circulation of hot water. This system is not sufficiently effective; however, as to a large extent the degree of cooling depends on the conditions outside the machine, which are extremely variable depending on the location of said machine, hence an excessively complex control mechanism would be required in order to determine the ideal circulation conditions. As a consequence of not providing said control mechanism, the aforementioned recirculation mitigates the cooling effects, but fails to provide a complete and effective solution to the problem.
An alternative, more effective solution consists of draining the pipes with each serving by inducing an air intake in the last part of each serving. Because no residual water remains in the pipes between two consecutive servings, appreciable improvements have been achieved with this system. A three-way electrovalve is disposed in the top part of the boiler in order to implement this solution. One of the ways is the water inlet from the boiler, another is the outside air inlet, and the third is the water outlet towards the dispenser.
Nevertheless this solution is not ideal: in each serving a volume of water is retained in the electrovalve seats, between the boiler and the pipes, and when this water cools down the disadvantage persists.
The technical problem consists of providing a hot beverage vending machine wherein after each serving no water remains outside the boiler and wherein in addition the amount of heat yielded by the elements outside the boiler after each serving and the amount of additional heat needed to maintain the hot beverage serving at the design temperature are minimized.